Pressure sensitive adhesive release liner

ABSTRACT

Pressure sensitive adhesives can be protected with a releasable liner having a cured fluoroalkyl silicone coating which contains as little as two percent fluoroalkyl-substituted siloxane units. In a preferred embodiment of this invention silicone pressure sensitive adhesives can be solvent-cast, and even cured, directly onto the release surface of the liner and can be removed from the protective liner with a force of no more than 400 grams per inch. The fluoroalkyl silicone copolymers of this invention are prepared by a process which involves the preparation of a cohydrolyzate of fluoroalkyl-containing and fluoroalkyl-free siloxane units, followed by further polymerization of the cohydrolyzate with other siloxane units.

This is a division of co-pending application Ser. No. 870,567, filed onJune 4, 1986, now U.S. Pat. No. 4,736,048.

BACKGROUND OF THE INVENTION

The present invention relates generally to the release of pressuresensitive adhesives, such as organic pressure sensitive adhesives andsilicone pressure sensitive adhesives, herein also called PSAs, OPSAsand SPSAs, respectively. In a particular aspect, this invention relatesto a method for coating a substrate to provide a release backing whichcan be used to protect SPSAs, to curable coating compositions thereforand to articles of manufacture comprising the cured coatings.

SPSAs, such as those disclosed in U.S. Pat. Nos. 2,736,721; 2,814,601;2,857,356; 3,528,940; 3,929,704; 3,983,298; 4,309,520; Canadian Pat. No.711,756 and British Pat. No. 998,232 are well known for their excellentthermal stability and tenacious adhesiveness. While these propertieshave valuable utility the adhesiveness, i.e. tack and/or adhesivestrength, of SPSAs is also a significant problem.

Whether the SPSA has the form of, for example, an adhesive layer on asubstrate in the form of a roll of tape; an adhesive layer on an articleprotected with a peelable backing, such as a decorative trim item to beadhered to an automobile or a medical item to be adhered to the skin ofa person; or a transfer adhesive layer protected on two surfaces bypeelable backings, the SPSA must be separated from an adjacent surfacebefore it can be used for its intended purpose.

Because of the above-noted and well-known tenacious adhesiveness ofSPSAs substantially every material that has been used as a protectivebacking or as a tape substrate for SPSAs has been given some sort ofsurface treatment to facilitate the removing of the adjacent surfacefrom the adhesive without adhesive separation or transfer and with aforce sufficiently small to avoid the tearing of the substrate, item orbacking.

Keil, U.S. Pat. No. 3,050,411, employed a dispersion of a mixture of amethylhydrogenpolysiloxane, certain fluoroalkyl-substituted siloxanesand a curing catalyst as a surface release agent. The siloxanes had aviscosity of at least 5000 centistokes at 25° C. and consisted of atleast 90 mol % of fluorinated siloxane units having the formula RCH₂ CH₂Si(CH₃)O, wherein R is a perfluoroalkyl group having less than 4 carbonatoms, not more than 10 mol % of siloxane units having the formulaR'_(n) SiO.sub.(4-n)/2, a degree of substitution ranging from 1.9 to 2.0and at least two silicon-bonded hydroxyl or lower alkoxyl radicals.Keil's compositions were found to release SPSA tapes with ease andwithout loss of the adhesiveness of the SPSA; however, said compositionswherein R is CF₃ do not provide easy release of SPSAs which have beencast thereon from a solvent solution of the adhesive. In addition, saidcompositions do not provide suitable release of curable SPSAs that havebeen cast and cured thereon. Compositions wherein R was C₂ F₅ or amixture of CF₃ and C₃ F₇ were said to give similar results.

O'Malley, U.S. Pat. No. 4,039,707, noted that if the SPSA was of acertain type, i.e. a SPSA containing diphenylsiloxane units, thestandard release coatings based on dimethylsiloxanes that were used withOPSAs were suitable for use therewith as a release composition. However,it is known that dimethylsilicone coatings will not releasedimethylsiloxane-based SPSAs.

Olson, U.S. Pat. No. 4,472,480, proposed a release backing comprising aninsoluble polymer film having a plurality of perfluoroalkylene oxiderepeating units. When formed by in-situ polymerization of a monomersolution the polymer film was said to resist transfer to aggressivelytacky PSAs and to be exceedingly thin. Among the polymerizable monomersillustrated by Olson were monomers bearing acrylate, epoxy, isocyanateand hydrolyzable silane groups. When epoxy-containing monomers were usedepoxy-substituted silanes could be copolymerized therewith. Whenmonomers bearing hydrolyzable silane groups were used "silanes which maybe linear or cyclic" were said to be copolymerizable therewith.

Koshar, European Patent Application No. 165,059, dated Dec. 18, 1985,discloses a low energy release liner for SPSAs comprising thehydrosilylation reaction product of an ethylenically unsaturatedperfluoropolyether and a compound bearing silicon-bonded hydrogen atoms.

It is apparent from the above that the preparation of a completelyacceptable release backing for SPSAs is a long-lived problem thatcontinues to command research and development resources.

One reason for the continuing research and development on releasecoatings for SPSAs is that the preferred process for pteparing anarticle containing a PSA and a release backing, which process comprisescasting a solution of the PSA onto the release backing and then bondingthe article to the adhesive layer, aggravates the subsequent release ofa SPSA from the release backing to the extent that an unacceptably highrelease force is needed to separate the release backing from theadhesive and/or the SPSA has an unacceptably low adhesive force after ithas been separated from the release backing.

The use of this casting practice, instead of applying the releasebacking to an adhesive layer already formed on the article, isnecessary, for example, in the process of forming an adhesive transfertape. In this process the PSA is cast onto one release backing and asecond release backing is thereafter applied to the adhesive layer.Although it is necessary that the adhesive release from one of therelease backings more easily than from the other release backing, thegreater release force must not be so great as to result in cohesivefailure of the adhesive or tearing of the release backing.

The use of this casting practice is also necessary, for example, when anarticle to which a heat-curable PSA is bonded is sensitive to thetemperatures used in the curing process. In this case the PSA is castonto the release backing and heat-cured and then the heat-sensitivearticle is bonded to the adhesive layer.

Until the present invention there had been no release coatingcompositions that would release solvent-cast, curable SPSAs with anacceptable release force and without substantially altering theadhesiveness of the released SPSA.

Another reason for the continuing research and development on releasecoatings for SPSAs is the progress in the formulation of SPSAs. Forexample, curable SPSAs having an adhesive strength substantiallyexceeding 1,200 grams/inch, as measured by standard methods hereinafterdescribed, are now available. For another example, recently developedSPSAs that have resistance to amine-containing materials, such asmedicines, present new release problems, even though they requirerelease forces much less than 1,000 grams/inch. In this regard,reference is made to U.S. patent application Nos. 665,796; 665,797 and665,805, filed on Oct. 29, 1984 and 780,505, filed on Aug. 26, 1985,said applications being assigned to the assignee of the presentapplication.

An improved release backing for SPSAs, particularly solvent-cast SPSAs,and most importantly for solvent-cast, heat-curable SPSAs, is thusneeded in the adhesives industry.

BRIEF SUMMARY OF THE INVENTION

It is an object of this invention to provide a method for preparing animproved peelable protective backing for PSAs. It is a particular objectof this invention to provide a protective backing that can be used toreceive, and subsequently release, a solvent-cast SPSA. It is also anobject of this invention to provide a peelable protective backing thatcan be used with solvent-cast, heat-curable SPSAs. It is an additionalobject of this invention to provide a coating composition for preparinga surface that will release a PSA, particularly a solvent-cast SPSA. ltis a further object of this invention to provide an improved articlecomprising a layer of SPSA which is protected by a peelable backing.

These objects, and others which will be apparent upon considering thefollowing disclosure and appended claims, are obtained by the presentinvention which, briefly stated, comprises applying certain curablefluorosilicone compositions to a substrate and curing the appliedcomposition before it is brought into contact with a PSA.

The curable fluorosilicone composition comprises a fluorosiliconepolymer which will provide a durably adhered, fully cured coating havinga low surface energy and a high degree of molecular chain flexibility.

This polymer is mixed with a curing agent and coated and cured onto asubstrate for the purpose of releasing normally tacky adhesivessubsequently adhered thereto. Certain forms thereof, suitablyformulated, can be used to release solvent-cast, heat-cured SPSAs. Inview of the teachings of the art it was surprising to discover that theintroduction of as little as 2 mol percent of fluorinated siloxaneunits, in some instances, into a polydimethylsiloxane would change thepolydimethylsiloxane from a SPSA-holding to a SPSA-releasing material,when cured.

Surprisingly, it has been found that the method and composition of thisinvention succeed where the methods and compositions of the prior art,including the more highly fluorinated silicone compositions of Keil,fail; i.e. in the release of solvent-cast SPSAs, and even solvent-cast,heat-cured SPSAs, with a usable release force and a minimum of adhesivealteration.

DETAILED DESCRIPTION OF THE INVENTION

In a first aspect the present invention relates to a coating compositioncomprising a curable mixture consisting essentially of (A) afluorosilicone polymer containing an average of at least twosilicon-bonded curing radicals per molecule selected from the groupconsisting of hydrogen, hydroxyl and alkenyl and at least 2 mol percent,based on the total number of siloxane units in the fluorosiliconepolymer, of fluorinated siloxane units, any remaining siloxane units inthe polymer being non-fluorinated siloxane units: said fluorinatedsiloxane units having the formula (RQ)(R')_(a) (Z)_(b) SiO.sub.(3-a-b)/2and said non-fluorinated siloxane units having the formula (R')_(c)(Z)_(d) SiO.sub.(4-c-d)/2 where, in said fluorinated and non-fluorinatedsiloxane units, R denotes a perfluoroalkyl radical having from 4 to 8carbon atoms and, additionally, 2 to 3 carbon atoms when thefluorosilicone polymer contains less than 90 mol percent fluorinatedsiloxane units and additionally, 1 carbon atom when the fluorosiliconepolymer contains from 7 to 10 mol percent fluorinated siloxane units, Qdenotes a divalent hydrocarbon, hydrocarbon ether or hydrocarbonthioether radical linking the R radical to a silicon atom through atleast 2 carbon atoms, R' denotes a silicon-bonded, monovalenthydrocarbon radical free of aliphatic unsaturation, Z denotes saidsilicon-bonded curing radical, a=0 to 2, b=0 to 2, a+b=0 to 2, c=0 to 3,d=0 to 3 and c+d=0 to 3 and, (B) an effective amount of a curing agentfor the fluorosilicone polymer.

The fluorosilicone polymer (Component A) of the compositions of thisinvention is an organopolysiloxane consisting essentially ofsilicon-bonded curing radicals, fluorinated siloxane units and,optionally, non-fluorinated siloxane units.

The silicon-bonded curing radicals are selected from the groupconsisting of hydrogen atoms, hydroxyl radicals and alkenyl radicals,examples of the latter being vinyl, allyl, butenyl, pentenyl, hexenyl,octenyl and decenyl. Preferably the aliphatic unsaturation in thealkenyl curing radicals is in the terminal, i.e. omega position.

By fluorinated siloxane units it is meant siloxane polymer units thatbear a perfluoroalkyl radical suitably bonded to a silicon atom. Thefluorinated siloxane units have the formula (RQ)(R')_(a) (Z)_(b)SiO.sub.(3-a-b)/2, general examples of which include chain-terminatingsiloxane units having the formula (RQ)(R')_(a) (Z)_(b) SiO_(1/2), wherethe sum of a+b is 2, such as (RQ)(R')₂ SiO_(1/2), (RQ)(Z)₂ SiO_(1/2) and(RQ)(R')(Z)SiO_(1/2), chain-extending siloxane units having the formulae(RQ)(R')SiO_(2/2) and (RQ)(Z)SiO_(2/2) and chain-branching siloxaneunits having the formula (RQ)SiO_(3/2).

The non-fluorinated siloxane units, if present, have the formula(R')_(c) (Z)_(d) SiO.sub.(4-c-d)/2, general examples of which includechain-terminating siloxane units having the formula (R')_(c) (Z)_(d)SiO_(1/2) where the sum of c+d is 3, such as (R')₃ SiO_(1/2), (R')₂(Z)SiO_(1/2), (R')(Z)₂ SiO_(1/2) and (Z)₃ SiO_(1/2), chain-extendingsiloxane units having the above formula where the sum of c+d is 2, suchas (R')₂ SiO_(2/2), (R')(Z)SiO_(2/2) and (Z)₂ SiO_(2/2) andchain-branching siloxane units having the above formula where the sum ofc+d is 1 or 0, such as (R')SiO_(3/2), (Z)SiO_(3/2) and SiO_(4/2).

Although the fluorosilicone polymer can have any viscosity up to severalmillion centistokes, it is believed necessary that the polymer not be anon-fluid, such as a gel or a solid. Therefore, said chain-branchingsiloxane units, if present, should be present in only minor amounts.

It is preferred that the fluorosilicone polymer be made up of onlychain-extending and chain-terminating siloxane units selected from thegroup consisting of YMe₂ SiO_(1/2), RQMeYSiO_(1/2), MeYSiO_(2/2) andRQYSiO_(2/2) siloxane units; wherein Y denotes Me or A, A denotes anomega-alkenyl radical and Me denotes the methyl radical. The presence ofother chain-terminating and/or chain-extending siloxane units would leadto polymers that contain silicon atoms that bear a plurality of curingradicals, and would be expected to present synthesis, as well as curing,problems.

Specific examples of said selected siloxane units include, but are notlimited to, Me₃ SiO_(1/2), Me₂ ViSiO_(1/2), RQMe₂ SiO_(1/2),RQMeViSiO_(1/2), Me₂ SiO_(2/2), MeViSiO_(2/2), RQMeSiO_(2/2) andRQViSiO_(2/2), where R is, for example, perfluorobutyl.

General examples of preferred fluorosilicone polymers include, but arenot limited to, the following:

YMe₂ SiO(MeYSiO)_(m) (RQYSiO)_(n) SiMe₂ Y,

RQMeYSiO(MeYSiO)_(m) (RQYSiO)_(n) SiMeYRQ,

Me₃ SiO(Me₂ SiO)₀.95m (MeViSiO)₀.05m (RQMeSiO)_(n) SiMe₃,

ViMe₂ SiO(Me₂ SiO)_(m) (RQMeSiO)_(n) SiMe₂ Vi,

ViMeRQSiO(RQMeSiO)_(n) SiMeRQVi,

Me₂ RQSiO(RQMeSiO)₀.95n (RQViSiO)₀.05n and

Me₃ SiO(Me₂ SiO)_(m) (RQMeSiO)₀.90n (RQViSiO)₀.10n SiMe₃,

wherein the viscosity of the polymer ranges from that of a freelyflowing liquid to a slowly flowing gum and m and n have values of fromzero to 10,000 and more.

For the purpose of providing a fully cured coating on a substrate whichwill release SPSA, solvent-cast thereon, with a force of no more than200 grams per inch, it is preferred that the fluorosilicone polymer havea linear structure and in-the-chain curing radicals as represented bythe formula

    YMe.sub.2 SiO(Me.sub.2 SiO).sub.x [RCH.sub.2 CH.sub.2 Si(Me)O].sub.y (MeASiO).sub.z SiMe.sub.2 Y

wherein the values of x, y and z are each greater than zero and are suchthat the fluorosilicone polymer contains from 1 to 10 mol percentalkenyl-containing siloxane units, at least 5 mol percent fluorinatedsiloxane units and the balance dimethylsiloxane units.

For the purpose of providing a fully cured coating which will releasesolvent-cast heat-curable SPSAs with a force of no more than 200 gramsper inch it is preferred that the fluorosilicone polymer have a linearstructure and in-the-chain curing radicals as represented by the formulanoted immediately above wherein the values of x, y and z are eachgreater than zero and are such that the fluorosilicone polymer containsfrom 3 to 7 mol percent alkenyl-containing siloxane units, from 20 to 50mol percent fluorinated siloxane units and the balance dimethylsiloxaneunits, and has a viscosity of from 100 to 1000 centistokes at 25° C.

In addition to limiting the fluorosilicone polymer to such a structureit may also be necessary to limit the type and amount of curing agentthat is used in the curable composition, as delineated below.

The terminal Y radicals can be methyl or alkenyl, such as vinyl, withoutsignificantly altering the release properties of a release backing ofthis invention. However, it may be desirable that the terminal Yradicals be alkenyl under moderate curing conditions, such as low curingtemperatures, short curing times or attenuated curing catalyst activity.

In the above formulae for the fluorosilicone polymer and its siloxaneunits R denotes a perfluoroalkyl radical having from 4 to 8 carbon atomsover the complete range of from 2 to 100 mol % fluorinated siloxaneunits. It has been discovered that these compositions provide unexpectedrelease of solvent-cast SPSAs, in view of what the art teaches.Moreover, R additionally denotes a perfluoroalkyl radical having from 2to 3 carbon atoms over the complete range of 2 to less than 90 mol %fluorinated siloxane units since these compositions also provideunexpectedly low release of solvent-cast SPSAs. Additionally, when thefluorinated siloxane units are used in limited amounts of 7 to 10 molpercent, R additionally denotes a perfluoroalkyl radical having 1 carbonatom. The R radicals can be identical or different and can have a normalor a branched structure. Examples thereof include CF₃ --, C₂ F₅ --, C₃F₇ --, C₄ F₉ --, such as CF₃ CF₂ CF₂ CF₂ --, (CF₃)₂ CFCF₂ --, (CF₃)₃ C--and CF₃ CF₂ (CF₃)CF--; C₅ F₁₁ --, such as CF₃ CF₂ CF₂ CF₂ CF₂ --; C₆ F₁₃--, such as CF₃ (CF₂)₄ CF₂ --; C₇ F₁₄ --, such as CF₃ (CF₂ CF₂)₃ --; andC₈ F₁₇ --.

Although this invention has not been investigated with polymerscontaining perfluoroalkyl radicals larger than perfluorooctyl it isreasonable, and within the scope and spirit of the present invention,that R can be C₉ F₁₉ --, C₁₀ F₂₁ --, and larger. However, it is clearthat polymers containing perfluoroalkyl radicals containing 1 to 8carbon atoms, depending upon the amount of fluorinated siloxane units inthe fluorosilicone polymer, provide excellent results and that the useof larger perfluoroalkyl radicals would only provide incrementalimprovements at higher cost.

Each perfluoroalkyl radical is bonded to a silicon atom by way of Q, adivalent spacing radical containing carbon, hydrogen and, optionally,oxygen and/or sulfur atoms which are present as ether and thioetherlinkages respectively. The sulfur and oxygen atoms, if present, must bebonded to only carbon atoms.

Each Q radical can have any structure containing the elements listed;however, each is preferably an alkylene radical having a normal orbranched structure. Examples of suitable alkylene radicals include --CH₂CH₂ --, --CH₂ CH₂ CH₂ --, --CH₂ (CH₃)CH₂ --, --(CH₂ CH₂)₂ --, --CH₂(CH₃)CH₂ CH₂ -- and --CH(CH₃)CH₂ --.

Each fluorinated radical RQ, preferably has the formula RCH₂ CH₂ --.Advantageously, the R radicals need be no larger than the CF₃ CF₂ CF₂CF₂ -- radical in order to have a fluorosilicone polymer that providesthe desirable release of SPSAs when cured. Accordingly, thefluorosilicone polymers that are to be used in the curable compositionsof this invention preferably contain fluorinated siloxane unitsdelineated above whose RQ radicals have the structure CF₃ CF₂ CF₂ CF₂Q--, and most preferably CF₃ CF₂ CF₂ CF₂ CH₂ CH₂ --.

In the above formulae for the fluorosilicone polymer and its siloxaneunits R' denotes a silicon-bonded monovalent hydrocarbon radical,preferably having from 1 to 6 carbon atoms, and containing no aliphaticunsaturation. The R' radicals can be identical or different, as desired.Examples of suitable R' radicals include alkyl radicals, such as methyl,ethyl, propyl, isopropyl, butyl, hexyl, 2-ethylhexyl, octyl, isooctyland decyl; aryl, such as phenyl, tolyl, benzyl, beta-phenylethyl, andstyryl. To provide optimum release of SPSAs, it is believed necessarythat at least 90 percent, and preferably all, of the R' radicals in thefluorosilicone polymer be methyl radicals.

In the above formulae for the fluorosilicone polymer and its siloxaneunits Z denotes a silicon-bonded curing radical selected from the groupconsisting of hydrogen, hydroxyl and alkenyl, as delineated above.

In the above formulae for the siloxane units the values of a, b, c and ddenote integers, the values of which are as delineated.

The values of m, n, x, y and z for the linear fluorosilicone polymerdenote average values, as is well known in the art, and are such thatthe polymer contains the requisite amount of alkenyl-containing siloxaneunits and fluorinated siloxane units and has the desired viscosity at25° C. The values of m, n, m+n, x, y, z and x+y+z thus will varygreatly. depending on the fluorinated siloxane unit content, thestructure of the fluorinated radicals and the viscosity of the polymer.As the mol percent of fluorinated siloxane units in the polymer, and/orthe size of the fluorinated radicals therein, increases, the viscosityof the polymer increases.

While the values of x, y and z can be as small as one the values of xand y can range to 10,000 and more and the value of z typically islimited to a fraction, such as from 1/100 to 2/10, of the sum of x+y+z.

The fluorosilicone polymers can be prepared by any of several methodsdisclosed in the art or by the method of this invention, delineatedbelow.

For example, the hydroxy-terminated polymers can be prepared by themethod of Johannson U.S. Pat. No. 3,002,951 or Brown, U.S. Pat. No.3,179,619. The organo-terminated polymers can be prepared by the methodof Pierce et al., U.S. Pat. No. 2,961,425. The patents to Johannson,Brown and Pierce et al. are incorporated herein by reference to show howto prepare fluorosilicone polymers.

The vinyl-containing copolymers of the general formula

    YMe.sub.2 SiO(Me.sub.2 SiO).sub.x [RCH.sub.2 CH.sub.2 Si(Me)O].sub.y (MeASiO).sub.z SiMe.sub.2 Y,

wherein the values of x, y an z are each greater than zero, arepreferably prepared by the method of this invention, disclosed below.

Specific examples of preferred fluorosilicone polymers of thisinvention, and the preferred method of Brown, are disclosed in theexamples disclosed below.

When formulated with an effective amount of a suitable curing agent thefluorosilicone polymers of this invention can be cured, i.e. convertedto the no-smear, no-migration, no-rub-off state, as measured by testsdescribed below.

Suitable curing agents, Component (B), for Component (A) comprise acrosslinking agent, examples of which include, but are not limited to,aliphatically unsaturated compounds to react with silicon-bondedhydrogen curing radicals, and organohydrogen silicon compounds bearing aplurality of silicon-bonded hydrogen atoms to react with silicon-bondedalkenyl curing radicals and/or silicon-bonded hydroxy curing radicals.Additionally, the curing agent typically comprises a curing catalyst toaccelerate the reaction of the curing radicals with the crosslinkingagent, particularly at elevated temperature.

Examples of aliphatically unsaturated crosslinking agents includeorganosilicon compounds such as silanes and cyclic, linear and resinoussiloxanes which bear a plurality of silicon-bonded alkenyl radicals.

Examples of organohydrogen silicon crosslinking agents include anyorganosilicon compound which bears a plurality of silicon-bondedhydrogen atoms such as cyclic, linear and resinous siloxanes, such asmethylhydrogencyclopolysiloxanes having the unit formula MeHSiO_(2/2) ;linear methylhydrogenpolysiloxanes having the formulae Me₃SiO(MeHSiO)_(i) (Me₂ SiO)_(j) SiMe₃ and HMe₂ SiO(MeHSiO)_(i) (Me₂SiO)_(j) SiMe₂ H where i and j have values of zero or more; branchedsiloxanes such as (HMe₂ SiO)₄ Si and the fluorosilicone crosslinkersdisclosed by Holbrook in U.S. Pat. No. 3,344,160; and the resinouscrosslinkers disclosed by Blizzard et al. in U.S. Pat. No. 4,310,678,said patents being incorporated herein by reference to further teach thescope and synthesis of said fluorosilicone crosslinkers and saidresinous crosslinkers.

Examples of suitable, well known curing catalysts include, but are notlimited to, organoperoxides, platinum-group metals and their compounds,and tin and lead salts of carboxylic acids, such as stannous octoate anddibutyltin diacetate.

The curable compositions of this invention preferably comprise a curingagent which comprises a platinum-containing hydrosilylation catalyst anda methylhydrogenpolysiloxane having the formula Me₃ SiO(MeHSiO)_(e)SiMe₃ wherein e has a value of from 30 to 70. A particularly usefulplatinum-containing catalyst for the curable compositions of thisinvention is the chloroplatinic acid-vinylsiloxane complex disclosed byWilling in U.S. Pat. No. 3,419,593, hereby incorporated by reference.However, the platinum-containing catalyst can be any of the well knownmaterials that are effective for catalyzing the hydrosilylation reactionof silicon-bonded hydrogen atoms with silicon-bonded vinyl radicals.

The amount of curing agent to be used in the compositions of thisinvention is not normally critical, it only being necessary to have aneffective amount thereof to fully cure the composition, as measured bythe tests delineated below. Typically, an effective amount of a curingagent will contain a sufficient amount of crosslinking agent to provideone or more crosslinking radicals for every curing radical in thefluorosilicone polymer. When the curing agent comprises amethylhydrogenpolysiloxane it is preferred that sufficient thereof beused to provide from 1 to 10, preferably from 1 to 4, silicon-bondedhydrogen atoms for every curing radical in the fluorosilicone polymer.

Beyond the need for a complete cure it is usually desirable to use asufficient amount of a curing catalyst in the curable compositions ofthis invention to provide a rapid cure rate. The exact amount of saidcatalyst will depend on the particular catalyst that is used and is noteasily predicted. However, for chloroplatinic acid and its complexes, anamount sufficient to provide from 10 to 500 parts by weight of platinumfor every one million parts by weight of the fluorosilicone polymer isusually sufficient. Within this range routine experimentation can beused to determine the optimum amount of catalyst needed for anyparticular cure time.

The curable compositions of this invention can further comprise variousamounts of optional components that will not adversely limit the use ofthe cured composition as a coating composition for the release of PSAs.Examples thereof include reactive components, such as adhesion promotersto improve the bonding of the cured composition to a substrate andcatalyst activity attenuators to inhibit the activity of the catalyst atroom temperature; and unreactive components such as diluents to decreasethe viscosity of the curable composition.

Preferred diluents include halogenated solvents, such aschlorofluorocarbons; esters, such as ethyl acetate; ketones such asmethylisobutyl ketone; and ethers, such as dibutyl ether. Preferredcatalyst activity attenuators include methylvinylcyclosiloxanes; estersof unsaturated alcohols and/or unsaturated acids, such as diallylmaleate and bis-(2-methoxyisopropyl) maleate; acetylenic compounds, suchas methylbutynol; and ene-ynes, such as ethynylcyclohexene. The readeris referred to, for example, the disclosures of U.S. Pat. Nos.3,445,420; 4,256,870; 4,465,818 and 4,562,096, to further illustrate theoptional attenuator component of the compositions of this invention.

The compositions of this invention are particularly useful for coating asubstrate such as a flexible sheet, to render the substrate adhesivereleasing. Thus, in another aspect the present invention relates to amethod for providing a substrate with a coating that will releasepressure sensitive adhesives, said method comprising (i) applying to thesurface of said substrate a coating of a coating composition comprisinga curable mixture consisting essentially of (A) a fluorosilicone polymercontaining an average of at least two silicon-bonded curing radicals permolecule selected from the group consisting of hydrogen, hydroxyl andalkenyl and at least 2 mol percent, based on the total number ofsiloxane units in the fluorosilicone polymer, of fluorinated siloxaneunits, any remaining siloxane units in the polymer being non-fluorinatedsiloxane units; said fluorinated siloxane units having the formula(RQ)(R')_(a) (Z)_(b) SiO.sub.(3-a-b)/2 and said non-fluorinated siloxaneunits having the formula (R')_(c) (Z)_(d) SiO.sub.(4-c-d)/2 where, insaid fluorinated and non-fluorinated siloxane units, R denotes aperfluoroalkyl radical having from 4 to 8 carbon atoms and,additionally, 2 to 3 carbon atoms when the fluorosilicone polymercontains less than 90 mol percent fluorinated siloxane units and 1carbon atom when the fluorosilicone polymer contains from 7 to 10 molpercent fluorinated siloxane units, Q denotes a divalent hydrocarbon,hydrocarbon ether or hydrocarbon thioether radical linking the R radicalto a silicon atom through at least 2 carbon atoms, R' denotes asilicon-bonded, monovalent hydrocarbon radical free of aliphaticunsaturation, Z denotes said silicon-bonded curing radical, a=0 to 2,b=0 to 2, a+b=0 to 2, c=0 to 3, d=0 to 3 to 3 and c+d=0 to 3 and, (B) aneffective amount of a curing agent for the fluorosilicone polymer and,(ii) thereafter causing the applied curable mixture to cure.

In the method of this invention the above-delineated curable compositionof this invention, including preferred embodiments thereof, is appliedto a substrate and cured thereon. The cured coating bonds to thesubstrate with a force greater than the force needed to remove anadhesive from the coating. The exposed surface of the cured coating isavailable to receive a normally tacky adhesive, such as a SPSA, and iscapable of releasing the adhesive with a force less than, preferably nomore than 80% of, its adhesive release force from stainless steel and,with certain compositions, with a force of no more than 400 grams perinch (154.4 newtons per meter), as measured by the Keil methoddelineated below, and without decreasing the adhesiveness of the PSA bymore than 25 percent.

Any solid substrate can be coated by the method of this invention;however the substrate is typically a flexible sheet material that is tobe peeled from a PSA which has been brought into contact therewith.Alternatively, the substrate can be an inflexible substrate to which anadhesive-bearing item is to be adhered and from which it is to besubsequently removed.

As to composition the substrate can be any suitable material; such assynthetic polymer materials such as polyolefins, polyesters, polyamides,polycarbonates, polyacrylates and polysiloxanes; cellulosic materialssuch as paper, cardboard and wood; metallic materials such as aluminum,steel, copper and silver; and siliceous materials such as glass, tile,ceramic and porcelain.

As to form the substrate typically has a flexible form such as apolymeric film, metal foil, polymeric film-coated metal foil, paper andpolymeric film-coated paper. However, as noted above, the substrate canalso be an inflexible material, such as metal or glass panel.

The curable composition can be applied by any suitable manner such as bybrushing, spreading, spraying, rolling, gravure, kiss roll, air knife ordoctor blade.

Once applied the coating composition is caused to cure, typically withthe use of heat to accelerate the curing reaction. Any solvents thatmight be present in the applied coating should be removed from thecoating before it is fully cured.

The resulting coated substrate will release PSAs which are brought intoadhesive contact therewith. The PSA can be applied to the coatedsubstrate in solution form and the solvent removed therefrom.Alternatively, the PSA can be first devolatilized and then brought intocontact with the coated substrate.

In a preferred embodiment the method of this invention is used to coat aflexible release backing, after which the coating is cured and asolution of a PSA is cast thereon. The PSA can be any of the well knownadhesives that are used in the art today; such as organic PSAs (OPSAs),such as acrylic-based adhesives and rubber-based adhesives; and siliconePSAs (SPSAs), such as those disclosed in the references noted above. Anyof the curable compositions of this invention, delineated above, willrelease these cast PSAs with a force of no more than 80% of its adhesiverelease force from stainless steel.

However, if it is desired to release an uncured, solvent-cast SPSA witha force of no more than 200 grams per inch or a heat-cured, solvent-castSPSA with a force of no more than 400 grams per inch, it appearsnecessary to limit the curable composition to one wherein thefluorosilicone polymer has the formula

    YMe.sub.2 SiO(Me.sub.2 SiO).sub.x [RCH.sub.2 CH.sub.2 Si(Me)O].sub.y (MeASiO).sub.z SiMe.sub.2 Y,

as delineated above, where the values of x, y and z are each greaterthan zero and are such that the fluorosilicone polymer contains from 1to 10 mol percent of the alkenyl-containing siloxane units, at least 5mol percent of the fluorinated siloxane units and the balancedimethylsiloxane units, and the curing agent comprises a mixture of aplatinum-containing hydrosilylation catalyst and amethylhydrogenpolysiloxane having the formula Me₃ SiO(MeHSiO)_(e) SiMe₃wherein e has a value of from 30 to 70.

If it is desired to release a solvent-cast, heat-cured SPSA with a forceof no more than 200 grams per inch, it appears necessary to limit thecurable composition to one wherein the fluorosilicone polymer has theformula

    YMe.sub.2 SiO(Me.sub.2 SiO).sub.x [RCH.sub.2 CH.sub.2 Si(Me)O].sub.y (MeASiO).sub.z SiMe.sub.2 Y,

as delineated above, wherein the values of x, y and z are each greaterthan zero and are such that the fluorosilicone polymer contains from 3to 7 mol percent of the alkenyl-containing siloxane units, from 20 to 50mol percent of the fluorinated siloxane units and has a viscosity offrom 100 to 1000 centistokes at 25° C. and the curing agent comprises aplatinum-containing hydrosilylation catalyst and amethylhydrogenpoly-siloxane having the formula Me₃ SiO(MeHSiO)_(e) SiMe₃wherein e has a value of from 30 to 70.

Even so the release of heat-cured, solvent cast SPSAs with the statedrelease forces is not guaranteed; it is merely made possible with thelimited compositions of this invention. It is necessary to apply thecurable release coating to the substrate in a sufficiently thick layerand in a sufficiently uniform manner to substantially coat the entiresurface of the substrate that is to be contacted with the solvent-cast,heat-curable SPSA. While this manner of coating is relatively easy forsome substrates, such as hard, smooth substrates that are easily wettedby the coating composition, it requires more attention when thesubstrate is porous and/or rough and/or resistant to wetting by thecomposition.

In the method of this invention it is preferred to uniformly coat thesubstrate so as to provide a layer of cured composition having a weightof at least 0.1 pound per ream, preferably at least 0.3 pound per ream,and most preferably from 0.5 to 1.0 pound per ream of flexiblesubstrate: a ream being equal to 3,000 square feet of coated surface.While it is possible to use heavier coating weights there is noadvantage in doing so and, at least from a cost viewpoint, isundesirable.

The flexible release backing of this invention has been invented to beused to protect PSAs and, in particular, SPSAs. Thus, in a relatedaspect the present invention relates to a laminated article ofmanufacture comprising a layer of pressure sensitive adhesive and thecoated substrate of this invention, releaseably adhered by a coatedsurface thereof to at least a portion of the layer of pressure sensitiveadhesive.

The PSA can be, for example, a free layer that is to be transferred to asupport. In this type of laminated article the laminate typicallyfurther comprises a second release layer that is in contact with thePSA, such as the next turn if the article has the form of a roll or aseparate release backing if the article has the form of a sheet. In anyevent the laminate possesses the property of differential releasewhereby one of the release layers is more easily released from the PSAthan the other release layer. The composition and method of thisinvention are particularly useful in preparing laminates of this typebecause differing release forces are available through the use ofcoating compositions having different release forces. Additionally,differing release forces are inherently available with any one coatingcomposition when the PSA is solvent-cast onto one coated substrate andbrought into adhesive contact with another substrate, identicallycoated, after it has been freed of solvent and, optionally, cured. Ofcourse, a combination of these two methods can also be used to providedifferential release.

The PSA can be, for example, durably adhered to an item that is to beultimately adhered to a support. Examples thereof include, but are notlimited to, medical items, such as transdermal drug delivery items, suchas nitroglycerine patches for the control of angina pain anddimenhydrinate patches for the control of motion sickness, and ostomydevices; trim items, such as decorative emblems and protective stripsthat are applied, for example, to vehicles; and decals, such asinstrument panel templates and labels. As noted above, these articlescan be prepared by applying the PSA to the release backing andthereafter durably adhering the item to the PSA, or vice versa.

The compositions, methods and articles of this invention are based, inpart, on novel fluorosilicone copolymers. Although the art disclosesmany fluorosilicone copolymers, the alkenyl-containing copolymers ofthis invention are not apparent therein.

Thus, the present invention further relates to a fluorosiliconecopolymer having the formula

    YMe.sub.2 SiO(Me.sub.2 SiO).sub.x [RCH.sub.2 CH.sub.2 Si(Me)O].sub.y (MeASiO).sub.z SiMe.sub.2 Y

wherein Y denotes Me or A, A denotes an omega-alkenyl radical, Medenotes the methyl radical, R denotes a perfluoroalkyl radical havingfrom 1 to 8 carbon atoms, the values of x, y and z are each greater thanzero and are such that the fluorosilicone polymer contains from 1 to 10mol percent alkenyl-containing siloxane units, at least 2 mol percentfluorinated siloxane units and the balance dimethylsiloxane units.

The several symbols that are used to delineate the fluorosiliconepolymers of this invention have the general and preferred meaningsdenoted above. In addition, the preferred fluorosilicone polymers ofthis invention are the same as those delineated above for the curablecompositions of this invention.

As stated above, the copolymers of this invention can be prepared by theprocess of this invention. Said process comprises (I) hydrolyzing amixture comprising one or more fluorinated silanes having the formula(RQ)(R")_(f) SiX .sub.(3-f) and one or more non-fluorinated silaneshaving the formula R"_(g) SiX.sub.(4-g) where, in said fluorinated andnon-fluorinated silanes, R denotes a perfluoroalkyl radical having from1 to 8 carbon atoms, Q denotes a divalent hydrocarbon, hydrocarbon etheror hydrocarbon thioether radical linking the R radical to the siliconatom through at least 2 carbon atoms, R" denotes a silicon-bondedradical selected from the group consisting of monovalent hydrocarbonradicals and hydrogen atoms, f has a value of 0, 1 or 2, g has a valueof 0, 1, 2, or 3 and X denotes a silicon-bonded hydrolyzable radical,(II) mixing with the hydrolyzed mixture obtained in (I) anorganopolysiloxane having the average unit formula R"_(h)SiO.sub.(4-h)/2 wherein R" has the meaning noted above and h has anaverage value of from 1 to 3 and (III) contacting the mixture of (II)with an effective amount of a silocane-equilibrating catalyst for aperiod of time sufficient to form the desired fluorosilicone polymer.

In step (I) of the process of this invention a cohydrolyzate of amixture of fluorinated and non-fluorinated silanes is first preparedwhich has greater compatibility with polydimethylsiloxanes than does thehydrolyzate of the fluorinated silanes alone. It has been found thatcohydrolyzates having as much as 90 percent fluorinated siloxane unitshave this improved compatibility with polydimethylsiloxanes. However, itis desirable to incorporate as much non-fluorinated silane into thehydrolyzate as possible, based on the composition of the polymer to beprepared and the compatibility of the silanes. Thus, for the purpose ofpreparing fluorosilicone polymers of this invention containing up to 50mol percent fluorinated siloxane units it is preferred to prepare acohydrolyzate having up to two fluorinated siloxane units for every onenon-fluorinated siloxane unit and then to introduce any additionalnon-fluorinated siloxane units, into the cohydrolyzate in the secondstep of this process.

The silanes that are mixed and cohydrolyzed in (I) bear at least onehydrolyzable radical (X) per molecule. Although the hydrolyzableradicals are preferably chlorine atoms it is believed that they can alsobe any other halogen atom, an alkoxy radical such as methoxy or ethoxy.an acyloxy radical such as acetoxy or an amino radical such as NH₂ orNH. Examples of suitable fluorinated silanes include RQMeYSiX andRQYSiX₂, such as RQ(Me)SiCl₂, RQ(Vi)SiCl₂, RQ(Me)₂ SiCl andRQ(Me)(Vi)SiCl. Examples of suitable non-fluorinated siloxane unitsinclude YMe₂ SiX and MeYSiX₂, such as Me₂ SiCl₂, MeViSiCl₂, Vi(Me)₂ SiCland Me₃ SiCl.

The silanes are preferably dissolved in a water-insoluble solvent suchas a dialkylether and the resulting solution added to water withvigorous agitation. If halosilanes are not used it is preferred that thewater be made acidic with a mineral acid such as hydrochloric acid.

The resulting hydrolyzate is then freed of any solvent and mixed with anorganopolysiloxane having the formula R"_(h) SiO.sub.(4-h)/2, examplesof which include cyclic siloxanes having the formulae (Me₂ SiO)_(i) and(MeASiO)_(i), wherein i has a value of at least 3, such as [(Me)₂SiO]₃₋₁₀ and [(Me)(Vi)SiO]₃₋₁₀ ; and linear siloxanes having the formulaYMe₂ SiO(Me₂ SiO)_(j) (MeViSiO)_(k) SiMe₂ Y, wherein j and k have valuesof zero or more, such as Me₃ SiO(Me₂ SiO)₀₋₁₀ (MeViSiO)₀₋₁₀ SiMe₃ andViMe₂ SiO(Me₂ SiO)₀₋₁₀ (MeViSiO)₀₋₁₀ SiMe₂ Vi.

The mixture of hydrolyzate and organopolysiloxane is brought intocontact with a siloxane-equilibrating catalyst such as an acidiccatalyst such as sulfuric acid-treated clays or ion-exchange resins,fluoroalkanesulfonic acids, perfluoroalkanesulfonic acids or mineralacids such as hydrochloric acid or sulfuric acid; or a basic catalystsuch as alkali metal hydroxides, alkali metal silanolates or tetraalkylammonium or phosphonium hydroxides or silanolates. The temperature ofthe mixture that is contacted with the acid is not critical sincecopolymer formation will occur at room temperature if a sufficientamount of time is allowed for the reaction to occur. However, it ispreferred to accelerate this reaction by heating the reaction mixture,for example to 100° to 200° C.

After the fluorosilicone polymer has been formed, as indicated by nofurther change in the viscosity of the reaction mixture, the catalyst ispreferably deactivated, such as by neutralization; although this step isnot necessary. It is also desirable, but not necessary, to removevolatile materials from the fluorosilicone polymer before it is used ina curable composition of this invention.

The following examples are disclosed to further teach how to practicethe present invention and should not be taken as limiting the invention,which is properly delineated by the appended claims.

All parts and percentages are by weight unless otherwise noted. Me andVi denote methyl and vinyl, respectively. Temperatures are degreesCelsius. Viscosities are at 25° Celsius.

The state of cure of an adhesive-release coating was determined by theruboff, migration and smear tests.

Smear was measured by lightly rubbing the coating with a finger andobserving the coating for a hazy appearance. The amount of haze wasestimated and rated as none, very slight, slight, moderate or gross. Afully cured coating displays no haze and therefore has no smear.

Ruboff was measured by vigorously rubbing the coating with the indexfinger tip, trying to remove the coating from the paper. The amount ofruboff was estimated and rated as none, very slight, slight, moderate orgross. A fully cured coating displays no ruboff.

Migration was measured by placing a strip of No. 610 Scotch1/2 brandtransparent tape on the coating, adhesive-bearing surface in contactwith the coating, and rubbing the strip 5 to 20 times with a finger toadhere the strip to the coating. The strip was then removed and itsadhesive-bearing surface doubled back on itself and slowly separated.The difference in force, relative to the force needed to separate adoubled, unexposed strip, was then estimated and rated as none, veryslight, slight, moderate or gross. A fully cured coating displays nodifference and thus has no migration.

Subsequent Adhesion of an adhesive that had been removed from a releasesurface was measured by applying the adhesive to a clean stainless steelpanel and measuring the force required to remove the tape therefrom.

Adhesion of an adhesive was measured by applying the adhesive, that hadnever been applied to a release surface, to a clean stainless steelpanel and measuring the force required to remove the tape therefrom.

The following adhesives are referenced in the following examples.

Adhesive No. 1--A non-curing SPSA available from Dow Corning Corporationas Dow Corning1/2 355 Adhesive.

Adhesive No. 2--A non-curing SPSA available from Dow Corning Corporationas Dow Corning 1/2 X7-3355 Adhesive.

Adhesive No. 3--A curable SPSA available from Dow Corning Corporation asDow Corning1/2 Q2-7330 Adhesive.

Adhesive No. 4--A SPSA tape prepared by applying and curing Adhesive No.3 onto 2-mil polyester film.

Adhesive No. 5--An amine-resistant, non-curing SPSA available from DowCorning Corporation as Dow Corning1/2 X7-2920 Adhesive.

Adhesive No. 6--A SPSA tape prepared by applying and curing GE1/2 590Adhesive, available from General Electric Company, to polyimide film.

Adhesive No. 7--A SPSA tape prepared by applying and curing Adhesive No.3 onto 1-mil polyimide film.

EXAMPLES 1A to 9I

These examples illustrate the present invention, including the processfor synthesizing a fluorosilicone polymer, several fluorosiliconepolymers, several curable compositions, the method for coating asubstrate to prepare a release liner for a silicone pressure sensitiveadhesive and a laminate of this invention. Example 1A uses Polymer A andComposition 1; Example 2B uses Polymer B and Composition 2, etc.

A mixture of 510.1 parts of heptane, 123.4 parts of Me₂ SiCl₂ and 517.7parts of (CF₃ CF₂ CF₂ CF₂ CH₂ CH₂)(CH₃) SiCl₂ was slowly added to 1348.5parts of stirred water. An exotherm to 55° resulted. The resultinghydrolysis mixture was stirred for 45 minutes and was then allowed tostand until a two-phase system resulted. The aqueous phase was separatedand discarded. The organic phase was washed once with 1000 parts of 10%aqueous NaCl, after which the organic phase was found to be neutral tolitmus paper. The heptane was then removed from the organic phase at apressure of 150 mm Hg and 40° to 55° and the residue was freed ofadditional volatile material by heating to 80° at maximum vacuum. Theresidue, 501 grams, was a copolymer of 60 mols of (CF₃ CF₂ CF₂ CF₂ CH₂CH₂)(CH₃)SiO_(2/2) siloxane units and 40 mols of (CH₃)₂ SiO_(2/2)siloxane units. This cohydrolyzate was used to prepare severalfluorosilicone polymers as follows.

A mixture of 294.62 parts of the 60/40 cohydrolyzate, 91.27 parts of[(Me₂)SiO]₄, 11.88 parts of [(Me)(Vi)SiO]₅, 2.23 parts of Me₃ SiO(Me₂SiO)₁₀ SiMe₃ and 0.4 part of CF₃ SO₃ H catalyst was heated at 70° for 5hours, after which it was cooled, mixed with 4 parts of NaHCO₃ and 5parts of diatomaceous earth and pressure-filtered. The filtrate wasdevolatilized at 150 degrees/2 mm Hg for 15 minutes. The fluorosiliconepolymer (Table 1, A) had a viscosity of 521 centistokes, 38.6 mol %fluorinated siloxane units and 4.4 mol % in-the-chain vinyl siloxaneunits.

In a similar manner, except for using appropriate amounts of theabove-noted siloxane reactants, the fluorosilicone polymers B to I,listed in Table 1, were also prepared.

A control polymer containing trimethylsiloxane units, dimethylsiloxaneunits and 4 mol % methylvinylsiloxane units was prepared byKOH-catalyzed equilibration of the appropriate cyclosiloxanes and thedodecasiloxane noted above.

Curable coating compositions of this invention were prepared by mixing 5parts of each of the polymers listed in Table 1 with 95 parts oftrichlorotrifluoroethane, 0.1 part of a complex ofdivinyltetramethyldisiloxane and H₂ PtCl₆ and a sufficient amount of Me₃SiO(MeHSiO)₅₀ SiMe₃ to provide the necessary amount of silicon-bondedhydrogen atoms. These compositions 1 to 9 are summarized in Table 2. Thecontrol composition was similarly coated and cured.

Each of these curable compositions was coated onto a piece of 2-milpolyester film using a #8 Mayer Rod and the coated film was heated at140° for 30 to 60 seconds to cure the coating. Thereafter solutions ofAdhesives 1, 2, 3 and 5, noted above, were cast onto the cured coatingsand onto an uncoated sample of film with a Bird Bar at a thicknesssufficient to provide a dry thickness of 1.5 mils of adhesive. Adhesives1, 2 and 5 were allowed to dry for 15 minutes before a 1 mil polyesterfilm was laminated to the adhesive using a 4.5 pound roller. Adhesive 3was given an additional heat-curing step for 5 minutes at 163° beforethe polyester film was laminated thereto. Adhesive 4 was applied as atape.

The laminates were evaluated for release by cutting the laminates into1×6 inch strips and the laminate was pulled apart at a rate of 12inches/minute using a Keil Tester. The values recorded in Table 2 arethe average of 5 readings taken during the course of one pull persample. The Keil Tester is described in TAPPI. Vol. 43, No. 8., pages164A and 165A (August 1960).

These examples illustrate that the compositions of this invention havingfrom 10 to 50 mol % fluorinated siloxane units readily releasesolvent-cast SPSAs with little or no loss of adhesion of the releasedadhesive. Additionally, compositions of this invention which containfrom 30 to 50 mol % fluorinated siloxane units release curable SPSAswith a force of less than 400 g/in. after having been solvent-cast andheat-cured thereon.

Of course it will be apparent to the practitioner of the PSA laminateart that the 2-mil polyester film can be replaced with a trim item, atransdermal drug delivery patch or a second release layer to produceadditional laminates of this invention.

                  TABLE 1                                                         ______________________________________                                        Polymer Composition, Mol %                                                    Poly-    Visc.,            RQ(Me)SiO,                                                                             Vi(Me)SiO,                                mer      cs.     D.P.      mol %    mol %                                     ______________________________________                                        A        521     329       38.6     4.4                                       B        176      86       30.0     5.2                                       C        660     426       49.8     6.9                                       D        2160    1017      31.0     2.9                                       E        365     162       29.5     3.3                                       F        870     438       47.4     8.8                                       G        145     742       53.4     5.5                                       H        6400    825       10.3     4.7                                       I        349     148       10.3     4.6                                       Con-     --      --        0        4.1                                       trol                                                                          ______________________________________                                    

                                      TABLE 2                                     __________________________________________________________________________                      Release, g/in.   S.A., g/in.*                               Comp.                                                                              Poly.                                                                            SiH/SiVi                                                                           Adh. 1                                                                             Adh. 2                                                                            Adh. 3                                                                            Adh. 4                                                                            Adh. 5                                                                             Adh. 1                                                                            Adh. 2                                                                            Adh. 3                                                                            Adh. 4                                                                            Adh.                       __________________________________________________________________________                                                       5                          1    A  4.00 5     5   56  5  17    946                                                                              324 746 618  870                       2    B  4.00 5    16  292 72  5    1114                                                                              258 780 988 1228                       3    C  2.50 5    26  222 90  5    1110                                                                              298 798 1022                                                                              1016                       4    D  3.25 5    126 270 48  5     742                                                                              258 676 942  660                       5    E  3.25 5     6  202 16  5    1060                                                                              274 688 938  806                       6    F  3.25 21   40  402 110 5    1126                                                                              312 674 1016                                                                              1226                       7    G  3.25 5    20  158 50  5    1134                                                                              284 828 844  822                       8    H  3.25 5    24  542 158 5    1152                                                                              310 722 1010                                                                              1112                       9    I  3.25 5    16  564 140 5    1268                                                                              308 722 976 1012                       Control                                                                            -- --   600  278 990 484 660   876                                                                              292 630 836 1024                       None -- --   1024 362 914 1288                                                                              1230 --  --  --  --  --                         __________________________________________________________________________     *S.A. = Subsequent Adhesion                                              

EXAMPLES 10J TO 18R

These examples illustrate the preparation of fluorosilicone polymershaving vinyl curing radicals in the chain and on the polymer ends and C₄F₉, C₆ F₁₃ or C₈ F₁₇ radicals bonded to silicon; the use of thesepolymers to prepare curable compositions and the use of thesecompositions to coat a substrate to release SPSAs. Example 10J usesPolymer J and Composition 10; 11K uses Polymer K and Composition 11,etc.

Thirty molar parts of C₈ F₁₇ CH₂ CH₂ Si(Me)Cl₂, 65 molar parts of Me₂SiCl₂ and 5 molar parts of MeViSiCl₂ were dissolved in an equal volumeof diethyl ether and the resulting solution was gradually added torapidly stirred water at a temperature of around 40°. The organic phasewas separated, was washed to neutrality and ether was removed bydistillation. The residue was mixed with 0.6 molar part ofvinyldimethylsiloxane-endblocked nonadimethylsiloxane and 2 percent byweight, based on the weight of the siloxanes, of a sulfonicacid-functional ion exchange catalyst and the mixture was heated at 115°for 4 hours and at 80° for 16 hours under a nitrogen purge to removewater. The resulting fluorosilicone copolymer (Table 3, J) was thenfiltered and devolatilized at 210° and 5 mm Hg.

In a similar manner, except for using appropriate amounts and types ofsiloxane reactants, the fluorosilicone polymers K to R, listed in Table3, were also prepared.

Nine coating compositions of this invention were prepared by mixing 4.75parts of a fluorosilicone polymer J to R with 0.24 part of themethylhydrogenpolysiloxane, 0.09 part of the catalyst and 94.92 parts oftrifluorotrichloroethane. The coating compositions were coated onto 2mil polyester film, the coatings were cured, the cured coatings wereoverlaid with SPSA and the SPSA laminated with polyester film, as notedin the above Examples. Release and Subsequent Adhesion testing was alsoperformed on these laminates and the results are summarized in Table 4.The comparison composition was Scotchpak1/2, a commercially availablerelease liner from 3M Company, Minneapolis, Minn.

                                      TABLE 3                                     __________________________________________________________________________    Polymer Composition, Mol %                                                    Poly.                                                                            R   (RCH.sub.2 CH.sub.2)(Me)SiO                                                              Me.sub.2 SiO                                                                       MeViSiO                                                                            ViMe.sub.2 SiO                                                                      Visc., cs.                                  __________________________________________________________________________    J  C.sub.8 F.sub.17                                                                  29.2       65.5 4.7  0.6   650                                         K  C.sub.8 F.sub.17                                                                  19.4       75.2 4.8  0.6   742                                         L  C.sub.8 F.sub.17                                                                  9.7        84.9 4.7  0.7   433                                         M  C.sub.6 F.sub.13                                                                  29.1       65.4 4.9  0.6   851                                         N  C.sub.6 F.sub.13                                                                  19.4       75.2 4.8  0.6   521                                         O  C.sub.6 F.sub.13                                                                  9.7        84.9 4.8  0.6   371                                         P  C.sub.4 F.sub.9                                                                   29.2       65.4 4.8  0.6   184                                         Q  C.sub.4 F.sub.9                                                                   19.3       75.2 4.8  0.7   126                                         R  C.sub.4 F.sub.9                                                                   9.7        84.9 4.8  0.6   140                                         __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________           Release, g/in.  S.A., g/in.*                                           Com.                                                                              Poly.                                                                            Adh. 1                                                                            Adh. 3                                                                            Adh. 7                                                                            Adh. 6                                                                            Adh. 1                                                                            Adh. 3                                                                            Adh. 7                                                                            Adh. 6                                     __________________________________________________________________________    10  J  5   190 100  32 1102                                                                              908 462 610                                        11  K  5   130 108  32  970                                                                              850 496 612                                        12  L  5   144  80  64  934                                                                              856 464 680                                        13  M  42  162 116 106 1012                                                                              902 458 634                                        14  N  64  166 116 134  824                                                                              836 466 640                                        15  O  118 290 136 158  998                                                                              828 438 636                                        16  P  80  238  82  90  982                                                                              820 454 674                                        17  Q  5   184  72 100 1016                                                                              826 432 654                                        18  R  5   192 138 218 1058                                                                              858 466 646                                        None                                                                              -- 928 914 450 618 1040                                                                              --  388 640                                        **  -- 8   428  5   10  846                                                                              758 446 606                                        __________________________________________________________________________     *S.A. = Subsequent Adhesion                                                   **Comparison Composition.                                                

EXAMPLES 19 AND 20

Fluorosilicone polymers containing 10, 20 and 30 mol percenttrifluoropropylmethylsiloxane units and 10 mol percentvinylmethylsiloxane units were prepared by heating a mixture oftrifluoropropylmethylcyclotrisiloxane, dimethylcyclotetrasiloxane,methylvinylcyclopentasiloxane and methyl-terminated dimethylnonasiloxanein the presence of 2 percent by weight, based on the weight of thesiloxanes, of CF₃ SO₃ H for 5 hours at 75°. The reaction product wasthen neutralized with NaHCO₃, filtered and devolatilized at 150° and 2mm Hg pressure.

A fluorosilicone polymer containing 7.5 mol percenttrifluoropropylmethylsiloxane units and 1 mol percentvinylmethylsiloxane units was similarly prepared except by using KOHinstead of CF₃ SO₃ H.

A fluorosilicone polymer containing 80 mol percenttrifluoropropylmethylsiloxane units and vinyldimethylsiloxaneterminating units was prepared similarly except the nonasiloxane wasvinyl terminated instead of methyl terminated andvinylmethylcyclopentasiloxane was omitted.

A hydroxyl-terminated fluorosilicone polymer containing 100 mol percenttrifluoropropylmethylsiloxane units and having a viscosity of 49,400 cswas prepared by heating trifluoropropylmethylcyclotrisiloxane in thepresence of KOH in the well known manner.

Six curable coating compositions were prepared by mixing 5 parts of eachof these polymers with 95 parts of trichlorotrifluoroethane and 0.1 partof a complex of divinyltetramethyldisiloxane and H₂ PtCl₆ and 0.25 partof Me₃ SiO(MeHSiO)₅₀ SiMe₃. The compositions were coated on polyesterfilm, cured, coated with adhesive and tested for adhesive release asdescribed above. The results of these experiments, summarized in Table5, show that compositions containing from about 7 to 10 mol percenttrifluoropropyl radicals release SPSAs with an unexpectedly low force.

                                      TABLE 5                                     __________________________________________________________________________    Polymer Composition, Mol % Release, g/in.                                     EB  Me.sub.2 SiO                                                                       (Me)(CF.sub.3 CH.sub.2 CH.sub.2)SiO                                                       (MeViSiO)                                                                           Adh. 1                                                                            Adh. 2                                                                            Adh. 5                                     __________________________________________________________________________    Me* 91.5 7.5          1     49  84  8                                         Me**                                                                              80   10          10     7  162 126                                        Me  70   20          10    942 432 1310                                       Me  60   30          10    680 458 900                                        Vi  19   80           l    1064                                                                              554 1114                                       OH***                                                                              0   100          0    242 212 230                                        __________________________________________________________________________     * = Example 19                                                                ** = Example 20                                                               *** = Composition of Keil, U.S. Pat. No. 3,050,411. Also releases Adhesiv     Nos. 3 and 4 with forces of 512 and 110 grams per inch, respectively.    

EXAMPLES 21 AND 22

A mixture of 500 parts of dibutylether, 3.81 parts of Me₂ SiCl₂, 16.65parts of MeViSiCl₂ and 479.54 parts of (CF₃ CF₂ CF₂ CF₂ CH₂CH₂)(CH₃)SiCl₂ was slowly added to 800 parts of stirred water. Afterbeing washed, filtered and devolatilized in the usual manner a 99.66portion of the hydrolysis product was mixed with 0.34 part of 2 cs.methyl-terminated polydimethylsiloxane fluid and 0.1 part of CF₃ SO₃ Hand heated at 70° for 3 hours. The reaction product was neutralized andfiltered to provide a fluorosilicone polymer containing 90 mol percentfluorinated siloxane units, 8 mol percent methylvinylsiloxane units and2 mol percent dimethylsiloxane units. A 95.53 part portion of thehydrolysis product was mixed with 4.08 parts ofdimethylcyclotetrasiloxane and 0.39 part of the 2 cs fluid and processas noted to provide a fluorosilicone polymer containing 75 mol percentfluorinated siloxane units, 7 mol percent methylvinylsiloxane units and18 mol percent dimethylsiloxane units. When these polymers were testedfor adhesive release as described in Example 1A the results shown inTable 6 were obtained. A comparison of these examples with those inTable 5 show that the compositions of this invention having up to 90 molpercent fluorinated siloxane units have unexpectedly good SPSA releasein view of the teachings of the art.

                  TABLE 6                                                         ______________________________________                                        Polymer Composition, Mol %                                                                           Release, g/in.                                                (Me)                    Adh.       Adh.                                Me.sub.2 SiO                                                                         (C.sub.4 F.sub.9 CH.sub.2 CH.sub.2)SiO                                                      (MeViSiO) 1    Adh. 2                                                                              3                                   ______________________________________                                         2     90            8         12   104   420                                 18     75            7         11    54   284                                 ______________________________________                                    

EXAMPLE 23

A fluorosilicone polymer containing 2 mol % fluorinated siloxane unitsand 10 mol % vinylmethylsiloxane units was prepared in the same manneras described in Examples 1A to 9I, except that a 50/50 hydrolyzate wasused instead of the 60/40 hydrolyzate. When this polymer was formulated,coated, cured and overlaid with adhesive as described above AdhesiveNos. 1, 2, 3, 4 and 5 were released with forces of 280, 106 , 1056, 418and 332 grams per inch, respectively. Thus, while this curablecomposition has little utility for providing a release coating forreleasing Adhesive No. 3 it is useful for releasing solvent-cast SPSAsof the non-curing type.

EXAMPLES 24 TO 26

When Composition Nos. 16P, 17Q and 18R were formulated with 0.12%, basedon the weight of the fluorosilicone polymer, of anorganohydrogensiloxane having the average formula Me₃ SiO(Me₂ SiO)₃(MeHSiO)₅ SiMe₃ instead of the one shown, the curable compositionprovided a coating that released Adhesive Number 3 with forces of 336,310 and 392 grams per inch, respectively.

EXAMPLE 27

A fluorosilicone polymer was prepared by copolymerizing 95 parts of the60/40 cohydrolyzate described in Example 1A, 29.43 parts of [(Me₂)SiO]₄,3.83 parts of [(Me)(Vi)SiO]₅, 3.58 parts of Me₃ SiO(Me₂ SiO)₁₀ SiMe₃ and0.66 part of KOH catalyst was heated at 140° for 5 hours, after which itwas cooled, mixed with 0.71 part of acetic acid and 5 parts ofdiatomaceous earth and pressure-filtered. The filtrate was devolatilizedat 200°/2 mm Hg for 15 minutes. The fluorosilicone polymer had aviscosity of 272 centistokes, 60.79 wt % fluorinated siloxane units and3.44 wt % in-the-chain vinyl siloxane units.

When this polymer was formulated, coated, cured and laminated withadhesives, as described in Example 1A, it was found to release AdhesiveNo. 1 with a force of 5 grams per inch and Adhesive No. 3 with a forceof 332 grams per inch.

EXAMPLE 28

Example 27 was repeated, except that the polymer had a viscosity of 590cs. and 65.34 wt % fluorinated siloxane units because, for itspreparation, only 1.79 parts of the 2 cs fluid was used and the amountof polydimethylcyclosiloxane was increased to 30.47 parts. Releasevalues of 5 and 328 grams per inch were measured for Adhesive Nos. 1 and3, respectively.

EXAMPLE 29

Example 27 was repeated, except that 0.04 part of tetrabutylphosphoniumsilanolate was used instead of the KOH. The resulting polymer had aviscosity of 203 cs. and contained 59.86 wt % fluorinated siloxane unitsand 3.44 wt % in-the-chain vinyl siloxane units. When this polymer wasformulated. coated, cured and laminated as noted in Example 1A AdhesiveNos. 1 and 3 were released with forces of 5 and 240 grams per inch,respectively.

EXAMPLE 30

A solution consisting of 31.17 parts of heptane, 1.59 parts of Me₃ SiCl,15.0 parts of Cl₂ MeSi(CH₂)₃ OCF(CF₃)₂ and 30.29 parts of Me₂ SiCl wasadded to 160.2 parts of rapidly stirred distilled water over a period of17 minutes and the resulting mixture was stirred for 1 hour. Thetwo-phase system was separated and the organic phase was washed with anequal weight of 10% aqueous NaCl. The dried aqueous phase was thentreated with 0.1 part of trifluoromethane sulfonic acid and heated at72° overnight. The solution was neutralized with NaHCO₃, filtered andfreed of volatile materials by heating to 150° at 10 mm of Hg pressureto give a polysiloxane having a viscosity of 36.5 centistokes. Thispolysiloxane, 10.32 parts, was then heated overnight at 70° with 3.18parts of polydimethylcyclosiloxane and 0.75 part ofpolymethylvinylcyclosiloxane, in the presence of CF₃ SO₃ H. The reactionmixture was neutralized, filtered and devolatilized at 200° and 40 mm ofHg pressure to provide a polysiloxane having 10 mol % fluorinatedsiloxane units and 6 mol % vinyl siloxane units which, when applied andcured to a substrate, released Adhesive Nos. 1, 2, 3, 4 and 5 withrelease forces of 5, 78, 670, 180 and 7 grams per inch, respectively.

EXAMPLE 31

A mixture of 0.048 part of Me₃ SiCl, 0.745 part of MeViSiCl₂, 9.0 partsof (CF₃)₂ CFO(CH₂)SiCl ₂, 37.21 parts of Me₂ SiCl₂ and 12.2 parts ofheptane was added to 53.5 parts of rapidly stirred water over a periodof 10 minutes and the resulting cohydrolyzate was stirred for 1 hour.The organic phase was separated, washed, filtered and devolatilized at80° and at a pressure of 50 mm of Hg. The residue was then treated with0.012 part of CF₃ SO₃ H at 70° for 17 hours and then with NaHCO₃ andfiltered. The filtrate was devolatilized to give a polysiloxane fluidhaving 30 mol % fluorinated siloxane units and 6 mol % vinyl siloxaneunits. This fluorosilicone fluid was found to release Adhesive No. 3with a force of 320 grams per inch when applied and cured onto apolyester film substrate.

That which is claimed is:
 1. A method for providing a substrate with acoating that will release pressure sensitive adhesives, said methodcomprising(i) applying to the surface of said substrate a coating of acoating composition comprising a curable mixture consisting essentiallyof(A) a fluorosilicone polymer containing an average of at least twosilicon-bonded curing radicals per molecule selected from the groupconsisting of hydrogen, hydroxyl and alkenyl and at least 2 mol percent,based on the total number of siloxane units in the fluorosiliconepolymer, of fluorinated siloxane units, any remaining siloxane units inthe polymer being non-fluorinated siloxane units; said fluorinatedsiloxane units having the formula

    (RQ)(R').sub.a (Z).sub.b SiO.sub.(3-a-b)/2

and said non-fluorinated siloxane units having the formula

    (R').sub.c (Z).sub.d SiO.sub.(4-c-d)/2

where, in said fluorinated and non-fluorinated siloxane units, R denotesa perfluoroalkyl radical having from 4 to 8 carbon atoms and,additionally, 2 to 3 carbon atoms when the fluorosilicone polymercontains less than 90 mol percent fluorinated siloxane units and 1carbon atom when the fluorosilicone polymer contains from 7 to 10 molpercent fluorinated siloxane units, Q denotes a divalent hydrocarbon,hydrocarbon ether or hydrocarbon thioether radical linking the R radicalto a silicon atom through at least 2 carbon atoms, R' denotes asilicon-bonded, monovalent hydrocarbon radical free of aliphaticunsaturation, Z denotes said silicon-bonded curing radical, a=0 to 2,b=0 to 2, a+b=0 to 2, c=0 to 3, d=0 to 3 and c+d=0 to 3 and, (B) aneffective amount of a curing agent for the fluorosilicone polymer and,(ii) thereafter causing the applied curable mixture to cure.
 2. A methodaccording to claim 1 wherein the fluorosilicone polymer consists ofsiloxane units selected from the group consisting of YMe₂ SiO_(1/2)siloxane units, RQMeYSiO_(1/2) siloxane units, MeYSiO_(2/2) siloxaneunits and RQYSiO_(2/2) siloxane units: wherein Y denotes Me or A. Adenotes an omega-alkenyl radical and Me denotes the methyl radical andthe curing agent comprises an organohydrogen silicon compound.
 3. Amethod according to claim 2 for providing a substrate with a coatingthat will release silicone pressure sensitive adhesives with a force ofno more than 200 grams per inch, wherein the fluorosilicone polymer hasthe formula

    YMe.sub.2 SiO(Me.sub.2 SiO).sub.x [RCH.sub.2 CH.sub.2 Si(Me)O].sub.y (MeASiO).sub.z SiMe.sub.2 Y

wherein the values of x, y and z are each greater than zero and are suchthat the fluorosilicone polymer contains from 1 to 10 mol percentalkenyl-containing siloxane units, at least 5 mol percent fluorinatedsiloxane units and the balance dimethylsiloxane units, and the curingagent comprises a platinum-containing hydrosilylation catalyst and amethylhydrogenpolysiloxane having the formula Me₃ SiO(MeHSiO)_(e) SiMe₃wherein e has a value of from 30 to
 70. 4. A method according to claim 3wherein the ratio of silicon-bonded hydrogen atoms to silicon-bondedalkenyl radicals has a value of from 1/1 to 4/1.
 5. A method accordingto claim 4 wherein the fluorinated siloxane units have the formula

    (CF.sub.3 CF.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2)(CH.sub.3)SiO.sub.2/2

and all A radicals are vinyl.
 6. A method according to claim 2 forproviding a substrate with a coating that will release silicone pressuresensitive adhesives, solvent-cast and heat-cured thereon, with a forceof no more than 200 grams per inch, wherein the fluorosilicone polymerhas the formula

    YMe.sub.2 SiO(Me.sub.2 SiO).sub.x [RCH.sub.2 CH.sub.2 Si(Me)O].sub.y (MeASiO).sub.z SiMe.sub.2 Y

wherein the value of x, y and z are each greater than zero and are suchthat the fluorosilicone polymer contains from 3 to 7 mol percent alkenylcontaining siloxane units, from 20 to 50 mol percent fluorinatedsiloxane units and the balance dimethylsiloxane units, and has aviscosity of from 100 to 1,000 centistokes at 25° C. and the curingagent comprises a platinum-containing hydrosilylation cataylst and amethylhydrogenpolysiloxane having the formula Me₃ SiO(MeHSiO)_(e) SiMe₃wherein e has a value of from 30 to
 70. 7. A method according to claim 6wherein the ratio of silicon-bonded hydrogen atoms to silicon-bondedalkenyl radicals has a value of from 1/1 to 4/1.
 8. A method accordingto claim 7 wherein the fluorinated siloxane units have the formula

    (CF.sub.3 CF.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2)(CH.sub.3)SiO.sub.2/2

and all A radicals are vinyl.